This application is the National Stage of International Application PCT/F100/00139 which was filed on Feb. 22, 2000 and designated the U.S. This International Application was published under PCT Article 21(2) in English.
The present invention relates to an antenna radiator consisting of two plate-like or film-like parts connected by their foot ends to each other and also to the supply connection of the antenna.
For instance, the base transceiver stations of mobile telephone systems use dipole antenna systems comprising dipole antennas adapted for one or more frequency ranges, e.g. 900 MHz and 1800 MHz. The antennas have relatively narrow radiators which consist of two parts extending to both sides of the supply point of the antenna. The antennas have been made e.g. by etching on a fiberglass circuit plate. The radiators of the antennas are relatively narrow.
Due to the high frequencies used in mobile telephone systems, the circuit plate on which the antenna construction has been etched causes dissipation. The dissipation is mainly due to a large current flowing at the foot of the radiator parts and to voltage losses occurring at the tips of the radiator parts. A drawback with present antennas is the magnitude of dissipation, which is a result of especially the fact that the radiator parts are narrow at the foot.
The object of the present invention is to eliminate the drawbacks of prior-art solutions and achieve a radiator structure especially applicable for use in base stations of mobile telephone systems. The antenna radiator of the invention is characterized in that, especially to reduce current and voltages losses, the radiator parts are substantially wider at the foot than at the tip.
An embodiment of the invention is characterized in that the radiator parts taper from the foot towards the tip.
When a radiator according to the invention is used, dissipation caused by the circuit plate is reduced because the wide foot part reduces the losses due to the current flowing in the foot. In addition, due to their narrow shape, the tips have a small contact area, thus producing only small voltage losses. Therefore, a good radiation efficiency is achieved.